#include <bits/stdc++.h>

using namespace std;

int n,m,indt,indsol;
int t[100003];
bitset<100003>viz;
vector<int>L[100003],L2[100003],sol[100003];

void Citire()
{
    int i,x,y;
    ifstream fin("ctc.in");
    fin>>n>>m;
    for(i=1;i<=m;++i)
    {
        fin>>x>>y;
        L[x].push_back(y);
        L2[y].push_back(x);
    }
    fin.close();
}

void DFS(int x)
{
    unsigned int i;
    int y;
    viz[x]=1;
    for(i=0;i<L[x].size();++i)
    {
        y=L[x][i];
        if(viz[y]==0)
            DFS(y);
    }
    t[++indt]=x;
}

void DFS2(int x)
{
    unsigned int i;
    int y;
    viz[x]=0;
    for(i=0;i<L2[x].size();++i)
    {
        y=L2[x][i];
        if(viz[y]==1)
            DFS2(y);
    }
    sol[indsol].push_back(x);
}


int main()
{
    Citire();
    int i,j;
    for(i=1;i<=n;++i)
        if(viz[i]==0)
            DFS(i);
    while(indt)
    {
        i=t[indt--];
        if(viz[i]==1)
        {
            indsol++;
            DFS2(i);
        }
    }
    ofstream fout("ctc.out");
    fout<<indsol<<"\n";
    for(i=1;i<=indsol;++i)
    {
        for(j=0;j<sol[i].size();++j)
            fout<<sol[i][j]<<" ";
        fout<<"\n";
    }
    return 0;
}